There is a growing demand for fine semiconductor devices and microelectromechanical systems (MEMS). Thus, a photo-nanoimprint technique is attracting attention as micro- and nano-fabrication technology.
In the photo-nanoimprint technique, a photocurable composition (resist) on a substrate (wafer) is cured while a mold having a fine uneven pattern on its surface is pressed against the substrate. The uneven pattern of the mold is transferred to a cured film of the photocurable composition on the substrate. The photo-nanoimprint technique can form a fine structure on the order of nanometers on substrates.
In a photo-nanoimprint technique described in PTL 1, a resist is first placed in a patterning region on a substrate (placement step). The resist is then patterned with a patterned mold (mold contact step). The resist is then cured by photoirradiation (photoirradiation step) and is removed (demolding step). Through these steps, a resist pattern (photocured film) having a predetermined shape is formed on the substrate (FIGS. 1A to 1D).
A substrate may be processed in a reverse process using a pattern formed by the photo-nanoimprint technique as a mask.
PTL 2 discloses the following steps. A reverse layer is formed on an uneven pattern (reverse layer forming step). While the recessed portions are filled with the reverse layer material, part of the reverse layer is removed to expose the top faces of the raised portions of the uneven pattern (reverse layer partial removal step). The reverse layer in the recessed portions is used as a mask. The layer having the uneven pattern and an underlying layer to be processed are etched through the mask to form a reverse pattern formed of the reverse layer material (etching step).